1. Field of the Invention
The present invention relates to heat exchangers in general, and more particularly, to heat exchangers adapted for use in cooling sealed electronics cabinets.
2. Description of the Related Art
Electronic equipment, such as telecommunications loop electronic equipment, is often housed in customized cabinets. The cabinets are generally placed out-of-doors, simply mounted on a concrete pad. Thus, the cabinets must be weather resistant and sealed to keep out water. The electronic components housed in the cabinet produce heat when operating. Therefore, a cooling system is required to remove the heat from the cabinets.
In U.S. Pat. No. 4,949,218 to Blanchard et al., which is hereby incorporated by reference in its entirety for all purposes, one such cabinet is proposed. As can be seen in FIG. 1, the Blanchard et al. cabinet 1 has an interior chamber 3 for housing electronic equipment. To cool the electronic equipment, heat exchangers 5 are provided. The cabinet 1 is sealed, having a top formed by diagonal plates 7 and longitudinal plate 9. Each of the heat exchangers 5 have a portion within the sealed cabinet and a portion within an air duct. As can be seen in FIG. 1, air vents 11 are provided, and fans 13 move air through the air vents, past the heat exchangers 5. The fans 13 are propeller fans. The system is a passive, closed system which does not introduce outside air and its associated moisture and contaminants into the interior chamber 3. The heat exchangers 5 of Blanchard et al. are extruded heat exchangers.
The design of the cooling system for the cabinet described above is deficient in that the heat transfer surface area of the heat exchangers 5 is limited by the extrusion fabrication process. Also, the cooling fins can be oriented only in the direction of extrusion. In addition, heat transfer enhancement features such as fin perforations or lances cannot be incorporated. Moreover, the propeller fans 13 have limited air flow rate capacity past the heat exchangers 5 as compared to some other types of fans.
Besides the heat exchanger cooling system disclosed in Blanchard et al., other heat exchanger cooling systems have been proposed. However, the heat exchangers of such systems generally do not meet the stringent design requirements of Bell Communications Research (Bellcore). These requirements include the ability to withstand harsh outdoor weather conditions. However, previous heat exchangers do not have optimal sealing between the exhaust side and the heat generating side.
Further, previous heat exchangers generally employ an epoxy resin for sealing the layers of heat exchanger fins to one another and to a separating plate. However, there are numerous problems associated with the use of epoxies, including decreased thermal conductivity. Also, because the coefficient of thermal expansion for adhesives, including epoxy adhesives, is quite different than that for the metal heat exchanger fins, an epoxy adhesive seal is susceptible to cracking or moisture retention.